TRYING TO UPDATE MY REGISTRATION WITH FAA FOR MY MAVIC AIR AND THEY WANT A REMOTE ID SERIAL NUMBER. DOESI HAVE ONE, I CAN'T SEEM TO FIND IT.

There are no remote iDs yet.  they are not out yet.

This might also help -

Hello there Krupman. Good day and thank you for the inquiry. For DJI drones already purchased, it is DJI’s hope to be able to provide software updates to its drones to make them compliant with Remote ID.

However, DJI must await finalization of technical requirements within the industry before determining which specific products it can upgrade via software updates to perform Remote ID. We may also need to prioritize the technical work for products that are being newly released in 2022, and that are still most popularly in use in mid-2023, which may be different from products being used today.

Regardless, the FAA will permit an add-on modules to perform Remote ID in the event DJI is unable to upgrade some of its drone products. For new drone products, during the next year, DJI will work to enable its products meet applicable Remote ID requirements by the relevant deadline.​ Thank you for your understanding and support. Thank you.

DJI Stephen Posted at 2021-10-12 20:57
Hello there Krupman. Good day and thank you for the inquiry. For DJI drones already purchased, it is DJI’s hope to be able to provide software updates to its drones to make them compliant with Remote ID.

However, DJI must await finalization of technical requirements within the industry before determining which specific products it can upgrade via software updates to perform Remote ID. We may also need to prioritize the technical work for products that are being newly released in 2022, and that are still most popularly in use in mid-2023, which may be different from products being used today.

It's nearly a year on.  Is the remote-id technology now available for a Mavic Air, and if so where to I get it?